Holocene sedimentation in a blue hole surrounded by carbonate tidal flats in The Bahamas: Autogenic versus allogenic processes.
Holocene sedimentation in a blue hole surrounded by carbonate tidal flats in The Bahamas: Autogenic versus allogenic processes.
复制标题
巴哈马碳酸盐滩涂包围的蓝洞中的全新世沉积：自生与异生过程。
DOI：
10.1016/j.margeo.2019.106051
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发表时间：
2020
期刊：
影响因子：
2.9
通讯作者：
van Hengstum, P. J.
中科院分区：
文献类型：
--
作者：
van Hengstum, P. J.
北大西洋蓝洞的沉积物保存了古气候记录。然而，准确的古气候重建需要一个更好的了解控制蓝洞沉积的异源与自生过程。在这里，我们提供了一个详细的淡水河蓝洞，这是目前所包围的碳酸盐潮滩在北方巴哈马群岛（阿巴科岛）内的全新世地层的案例研究。在全新世，伴随的沿海含水层的海拔和相对海平面上升控制内部蓝洞沉积环境。一般全新世相序列观察到的是：（i）基底碎屑和淡水泥炭，（ii）沼泽湖泥灰岩，（iii）藻腐泥，最后（iv）层状碳酸盐泥。在全新世中期，当地下水位较低时，继承自基岩表面（<1 m）的可容纳空间的微小变化能够促进显着的横向相变。需要多个岩心来表征这些侧向相变。沿海含水层的水文特征（例如，垂直位置、分层、盐度）对（a）底栖植物群和小型底栖生物（例如，轮藻、介形虫、有孔虫、腹足类）和（B）有机物质的生产和远洋生产力的保存。在过去的5000年里，淡水河蓝洞的水柱分层在千年到近十年的时间尺度上被中断，这可能与含水层补给和降雨量的变化有关。最后，历史上强烈的飓风从该地点以西附近经过，可能促进了该地点粗床的沉积。然而，缺乏碳酸盐潮滩微动物群仍然（有孔虫：Peneroplis）在这些粗间隔表明，淡水河蓝洞没有保存一个可靠的记录，在过去的2300年飓风引起的过冲沉积的碳酸盐潮滩。
The sediment in North Atlantic blue holes preserves paleoclimate records. However, accurate paleoclimate reconstructions require an improved understanding of allogenic versus autogenic processes controlling blue hole sedimentation. Here we provide a detailed case study of the Holocene stratigraphy within Freshwater River Blue Hole, which is currently surrounded by carbonate tidal flats in the northern Bahamas (Abaco Island). During the Holocene, concomitant coastal aquifer elevation and relative sea-level rise controlled internal blue hole depositional environments. The general Holocene facies succession observed is: (i) basal detrital and freshwater peat, (ii) palustrine to lacustrine marl, (iii) algal sapropel, and finally (iv) bedded carbonate mud. During the middle Holocene when groundwater levels were lower, small changes in accommodation space that were inherited from the bedrock surface below (<1 m) were able to promote significant lateral facies changes. Multiple cores are needed to characterize these lateral facies changes. Hydrographic characteristics of the coastal aquifer (e.g., vertical position, stratification, salinity) relative to the blue hole benthos exert a fundamental control on (a) benthic flora and meiofauna (e.g., charophytes, ostracodes, foraminifera, gastropods) and (b) organic matter production and preservation from pelagic productivity. Over the last 5000 years, water column stratification in Freshwater River Blue Hole was interrupted on millennial to sub-decadal timescales , which are potentially linked to changing aquifer recharge and rainfall. Lastly, historical intense hurricanes passing closely to the west of the site may have promoted deposition of coarse beds at the site. However, the lack of carbonate tidal flat microfaunal remains (foraminifera:Peneroplis) within these coarse intervals indicates that Freshwater River Blue Hole does not preserve a reliable record of hurricane-induced overwash deposition from the carbonate tidal flats during the last 2300 years.